This invention relates to a method of producing absorbent fibrous bodies. More particularly, this invention pertains to a method of producing absorbent components suitable for use in sanitary napkins, surgical dressings, compresses, disposable diapers, hospital underpads and other products for absorbtion of body fluids.
Products designed to absorb body fluids generally contain as a principal component thereof an absorbent panel, batt, pad or core. These panels or batts are normally made of layers of loosely compacted, absorbent fibers, such as carded cottom webs, air-laid cellulose fibrous webs, comminuted wood pulp batts, or like materials which are highly absorbent, fluffy and porous. Unfortunately, these loosely compacted fibrous absorbent bodies possess numerous disadvantages, such as low cohesive strength, poor shape and volume stability, low capillarity, low fluid retentivity and low absorptive capacities under conditions of use.
These fluffy, porous, absorbent fibrous components have the aforementioned shortcomings because of their loosely compacted structure. When a fluid is deposited on the surface of such a component, saturation conditions are reached very quickly at the site of immediate application. At the same time, however, the adjacent portions remain relatively unsaturated and, in some instances, dry due to the low capillarity of the fibrous body. Consequently, a highly localized fluid condition results.
When water-insoluble but absorbent particulate matter, such as hydrocolloid particles, are incorporated into a loosely compacted absorbent panel, in order to enhance the moisture retention thereof, these particles tend to "dust out" of the panel.
Commonly assigned U.S. Pat. Nos. 2,905,568, 2,955,641, and 3,017,304 to Burgeni describe a method by which the tensile strength of loose cellulosic fibrous fluff can be improved. According to the teachings of these patents, a controlled amount of water or an aqueous binder solution (between 0.0005 gms./cm..sup.2 and 0.03 gms./cm..sup.2) can be applied to one surface of the loose fiber mass, followed by a compacting pressure of between 5 psi and 100 psi to produce a densified bonded surface fiber structure or skin of water-induced, paper-like bonds, hereinafter sometimes referred to as a "Burgeni layer". Panels having a Burgeni layer have relatively good strength, good shape and volume stability and high fluid retentivity.
It has now been found, however, that a densified, absorbent fibrous layer can be produced in a pulp panel or batt without an external application of a water spray or the like as taught in the aforementioned Burgeni patents, and that during the formation of the densified layer hydrocolloid particles can be fixed within the panel to further enhance the fluid retentivity thereof.